Clad windows are designed to provide maintenance free exterior surfaces while maintaining a traditional wood interior. Typically the cladding material is a skin of aluminum or plastic preferably polyvinylchloride (PVC). PVC provides good weather-resistance but has shortcomings. Specifically, PVC cladding undergoes dimensional changes as the ambient temperature it is exposed to changes. The total change in length of a 6 foot length of PVC cladding can be as much as 7/16 of an inch. This expansion and contraction not only creates gaps in the cladding, but also results in large stresses at the corner sections. These high stresses are detrimental to the cladding because they can cause corner joints to open, welded corners to break and allows water to penetrate the system, degrading the wood substrate beneath the cladding.